This drama is actually promising with supernatural genre and intriguing theme: going against fate. Unfortunately, either the original webtoon storytelling is bad (I have not read it) or the script written for live adaptation is bad, the story ends up very confusing. I am sure a good script can fix a bad webtoon story to present it to us the smart viewers, am I not? Because I watched a few dramas adapted from webtoons and they are good.
Nothing wrong with the cast or acting, and I am not a fan of EXO or Suho to defend. I have watched several dramas with idol singers who are newcomers in acting in dramas, but they ended up good (for example Dating Class). In this case, a good director can direct even rookies to act well. Some said that actor Suho has acted in 2 dramas and 2 movies after HAYB (that were filmed in 2016) with better acting skill, and actress Lee Se Young's dramas after HAYB are all 8+ rated in MDL so far.

MAJOR SPOILER:
I am writing this part for people who are curious and confused about the story. So basically ML and FL meet 3 times minimum (unless there is any explanation I skipped). But their romance is supposedly not fated. If they insist then one of them will get hurt, according to the fat guy who is the guardian god of destiny who causes shaky camera scenes making us the viewers dizzy. This annoying god actually makes things happen to destroy their relationship too, including amnesia.
However, I actually suspect that the story writer dictates that the couple is fated because they keep meeting again and they always get revelation from their common dreams. By the end, the final scene is actually shown as hopeful and positive.